1. Field of the Invention
The invention relates to wireless communications, and more particularly, to locating a wireless device within a wireless telecommunication, system for communication purposes.
2. Description of the Related Art
In wireless telecommunication systems, Push-to-talk (PTT) capabilities are becoming popular with service sectors, PTT can support a “dispatch” voice service that operates over standard commercial wireless infrastructures, such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), and global system for mobile communications (GSM). In a dispatch model, communication between endpoints (end user devices) occurs within virtual groups, wherein the voice of one “talker” is transmitted to one or more “listeners.” A single instance of this type of communication is commonly referred to as a dispatch call, or simply a PTT call. A PTT call is an instantiation of a group, which defines the characteristics of a call. A group in essence is defined by a member list and associated information, such as group name or group identification. In the absence of a wireless multicast channel, each group is formed by the combination of separate point-to-point connections between each endpoint and application server. Each endpoint is also known as a PTT member. Alternatively, when a group is reduced to two members and a PTT call is from one member to another, the PTT call would be a direct call between these two members.
FIG. 1 illustrates a prior art architecture 100 supporting PTT communications. The architecture includes the deployment of a single application server 112 region in conjunction with a carrier's CDMA infrastructure and packet data network. Each region of the application server 112 is deployed over a specific portion of a carrier packet data network (“PTT Regional Network”) 110. The application server 112, also known as PTT server, within the region may be routing traffic between one or more Packet Data Service Nodes (PDSNs) 107 in the carrier network (Service Provider Regional Network) 108. A communication device 102 that supports the PTT feature is in communication with a base station controller (BSC) 104, which typically includes a base station (BS). Each BSC 104 may be in communication with one or more base station transceiver (BTS) 114. The BSC 104 is in communication with a high-speed network 106 and PTT communications received from the communication device 102 is sent through the BSC 104 and the high-speed network 106 to a PDSN 107. The BSC 104 may communicate with a package control function (PCF) 105 for processing data packets between the communication between the PDSN 107 and the communication device 102. The PDSN 107 communicates with the high-speed network 106 and an application server's 112 carrier network 108, which is connected to a PTT regional network 110. The PDSN 107 forwards the PTT communications to an application server 112 in the PTT network 110.
The application server 112 handles PTT communications among members of a PTT group. The application server 112 receives a PTT communication from one member and forwards it to all members of the PTT group. The PTT communication is usually received as data packets from the PTT network 110, and the PTT communication sent out by the application server 112 is also in data packet format. A PDSN 107 and a connected BSC 104 established through a BTS 114 have a dedicated traffic channel to transmit the PTT communication to a receiving PTT communication device (a PTT member) 102.
PTT communications are commonly used in public safety and disaster recovery scenarios in which a large number of public safety officers and rescue workers communicate among themselves through PTT communications. One of problems related to call set up for the PTT communications between a large number of users is the latency in during the call set up process.
The call set up involves locating a targeted PTT communication device 102 and allocating resources for each PTT communication and establishing a traffic channel to support each PTT communication. The location of each PTT communication device 102 is commonly tracked through location update messages sent from each PTT communication device 102 through a reverse traffic channel to the application server 112. When there are many simultaneously PTT communications in a small geographical area, such as during a public safety or disaster recovery situation, tracking the location of a plurality of PTT devices through location update messages has an adverse impact on the capacity of the wireless network due to increased resource usage (traffic channels need to be brought up frequently), as well as an increase in the network traffic. Consequently, lowered network capacity leads to additional delays during the call set up process. It is therefore desirous to have the PTT communication system that can easily and efficiently reduce the latency from ongoing location update messages when establishing multiple PTT calls.